If this were Nintendo then I’d agree but sega have always been really chilled about this so long as the community does t profit off their IP (which is a fair line to draw).

Because of this, you’ll fine tonnes of Sega fan stuff. From multiple active Phantasy Star Online servers through to entire fan-made Sonic games.

In fact iirc Sonic Mania started life as a fan game and Sega asked them to produce a full game.